OEM Lennox Dual Pressure Switch Assembly — 33W18
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The genuine OEM Lennox 33W18 dual pressure switch assembly proves combustion draft by confirming the inducer motor has created adequate negative pressure before allowing ignition. Its dual-switch design monitors venting across firing stages, serving as an essential safety control in compatible Lennox gas furnaces to prevent operation under unsafe venting conditions.
Common failure symptoms: When this switch fails, the furnace typically will not ignite, locks out on a draft-proving fault, or short-cycles with a flashing error code. Symptoms include the inducer running with no burner ignition, repeated failed start attempts, and heat that stops shortly after firing due to a switch stuck open or reading improper pressure.
Why OEM matters: The 33W18 is factory-calibrated to the exact pressure setpoints your Lennox furnace was engineered for. Substituting a generic switch with the wrong trip rating risks nuisance lockouts or, worse, firing without confirmed safe venting. Installing the genuine OEM part ensures correct calibration, proper fit, and dependable, safe furnace operation.
Shipping Information
- Orders placed before 3PM CST ship same business day
- Standard delivery: 2-5 business days
- Express shipping available at checkout
- Free shipping on orders over $75
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Return Policy
- 30-day returns on unused parts in original packaging
- Electrical parts (capacitors, contactors, control boards) are final sale once installed
- Email info@nationalhvacparts.com to initiate a return
- Refunds processed within 5-7 business days